casual day

Some offices designate a day, usually Friday, as casual day, when the formal styles usually demanded by professionalism can be ignored to a degree. You still have to dress neatly and non-offensively, but you can skip a bit of make-up and wear jeans if they don't have holes in them and wear sandals instead of polished leather. In short, you can pretend for a day that you work at a progressive techonology start-up instead of at an accounting firm where people look at you funny if your cufflinks don't match your lipstick.